In facilities for the continuous production of foam blocks of substantial width, it is known to attach a distributor member branching into a plurality of outlet pipes to the outlet of the mixing chamber. This distributor member is known in the art as an "antler". While this arrangement enables considerable quantities of mixture to be passed through per unit time due to the large cross sectional area available, there are generally no difficulties in the distribution of the mixture. In particular, exact quantitative distribution to the various outlet pipes is unimportant because the fluid mixture automatically becomes uniformly distributed on the inclined plane of the conveyor belt of the foaming installation.
It is also known to provide a distributor pipe system for the introduction of reaction mixture into very irregularly formed cavities enclosed by the two shells used for the manufacture of a bottom unit in motor vehicles so that the mixture can enter and flow uniformly to every point within the cavity. This distributor member can be connected to a mixing head on the outside. It is preferably constructed to serve also as reinforcing element for the surface shells.
Finally, in mixing heads which are combined with molding tools, it is known to sub-divide the sprue channel, by the usual method of extrusion and casting technology, into distributor channels which lead to the individual molding units.
With none of the known apparatus, however, is it possible to supply very small quantities of mixture to cavities, particularly open cavities.
When it is required to fill hollow building blocks with foam, for example, it is necessary to introduce relatively small quantities of mixture per unit time into the cavities. These quantities may vary from 10 to 100 g, according to the size of the cavity which is to be filled. The smallest foaming machines generally available on the market provide for a minimum feed time, generally known as shot time, of 0.5 seconds. If this is based on a quantity of mixture of 10 g, the total quantity ejected is 1200 g per minute. If, furthermore, it is assumed that the polyol and isocyanate components are used in the ratio of 1:1, the output of each pump is 600 g per minute. Such small quantities are difficult to control because of the difficulty of metering such quantities and especially because the forerun and afterflow adjustment is extremely troublesome. With a total shot time of 0.5 seconds, a forerun and afterflow even of only a few hundredths of a second are a considerable disadvantage.
The problem to be solved consists of finding a mixing head which can be used to introduce minute quantities of mixture into cavities.